Fab Academy 4

Electronics production

INDEX:

Here you will find an Index with links to easily navigate through the section content.

1

Intro:

The process for electronic production.

2

Mods Platform:

A little explanation about how to set the Mods platform.

3

SRM-20 Settings:

Instructions and tips for the use of the Roland SRM-20.

4

LED Badge:

Soldering Exercise. 

5

USB to FTDI:

Usb to FTFI soldering.

6

Other Programmers:

Some other programmers I built.

7

Soldering Tips:

Some tips I learned for a better soldering.

8

Machine Testing:

Testing the machine and end mill accuracy.

1 - INTRO:

This week we were learning electronic production. Not so much about designing the circuits, but more about cutting them in the milling machine and soldering them. We created a LED BADGE as a soldering exercise and a USB to FTDI PCB board's.

We Milled them in a SRM-20 milling machine, and for that, the first we had to do, was to prepare the files in the MIT MODS platform or Fabmodules.

I must say that I soldered the FTDI module and my partner soldered the LED BADGE (hehehhe)

USB to FTDI

LED BADGE

2 - Mods Platform:

Mods

Here I specify with images the basics of the Mods configuration, but I want to highlight some important things:

- It's important to know the thickness of your material and not using the preset always because that could also damage the end mill. Also if it falls it might break.

- The starting speed for a new end mill should be set to 3 the first time you use it if you are milling traces. Remember also to set the speed of the milling to 0.5 if you are doing outlines.

- The jog height needs to be at least 2mm above the 0 so that the end mill doesn't breaks of scratches the material, this also for the Z home. I would recommend to have it at 5mm - 10mm. If you put it to high, it will loose a lot of time going up and down each time it moves.

- You should check if the image you uploaded need to be inverted. That is going to depend on the way you exported it.

- The resolution should be set to around 1000 (999), also when exporting the file.

- The Offset number is relative to the amount to material to remove (or leave), and it should be set to 1 when doing outline and when doing in traces it can be set from 0 to 4, being 0 to leave the PCB really clean and without the material that is not needed.


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3 - SRM-20 Settings:

The most important thing for me in the setting of the machine, is to properly set the X, Y and Z (most of all the Z) since from that depends also that you don't break your end mill.

The X and Y you can set them with the Jog until you move the machine to the desired position and set the X,Y origin.

For the Z, you have to lower it slowly (10x max) until you arrive really close to the material. After that you should release the end mill from the machine and let it touch the material and then set the Z origin. Sometimes you have to put it a little bit lower so it properly cuts the material.

Then in the setup, you load the files in the order to be milled. First the inner parts (traces), then the holes, then the outer cut.

We used 1/64 end mill for the traces and 1/32 for the outline. One tip I use to change the end mills is to cover them with the blue cover they have while changing them so if they fall they don't break.

You can start at medium speed while checking everything is ok, and then put it to full power.

Even dough this is a machine that you can leave working alone, it is important to pay attention to the first minutes and every once in a while to see that everything is set and working correctly because sometime it could not be removing enough material, or it could be cutting in the air, or not taking in count some lines because of the thickness or how close it is one to the other.

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4 - LED BADGE:

Generated in Mods

We use this board as an initial soldering practice, before switching to the  USB to FTDI, which has more complicated components such as the microcontroller.

For this we had to use 10 LEDS, and we decided to use 5 red and 5 green to have variety. We also decided to use different types of resistors such as 200 OHMs, 100 OHMs, 49.9 OHMs, 10 OHMs and 1 OHMs, to see the difference generated by them.

5 - USB to FTDI:

Generated in Mods

SOURCE: Learn Adafruit

There are two ways to program an AVR microcontroller. One is to reprogram the entire chip using an AVR programmer. The other is to use a bootloader that is pre-programmed onto the chip that allows the chip to re-program itself. An AVR programmer is more powerful: you can really mess with anything on the chip and the entire 32K of memory is available. Using the bootloader is safer: there's no way to mess with the fuse settings (which could brick the chip) but you only get 30K of memory since 2K is used by the bootloader. Not a big deal, but if you are working on a big project which requires tons of flash space, you may need it.

AVR programmers are more powerful in that you can program any AVR, even blank ones from the factory. But that also means you have a pretty good chance of 'bricking' the chip!

FTDI adapters can send any serial data back and forth including updating AVRs with a bootloader on them. But you need to get that bootloader on there first, which basically requires an AVR programmer.

6 - Other Programmers:

Hello.serial-UPDI and a Hello.ISP.44

For this assignment, I also build an hello.serial-UPDI and a  hello.ISP.44 so that I could program AtTinny 44 and 1614 for other projects I did for the inputs and outputs week. Here I'm just going to upload some pictures of them.

7 - Soldering Tips:

Soldering is one of this things that you get much better the more you do it. When I did this assignment it took me around one hour to be able to solder the FTDI, but after the time I have managed to do it faster.

Now is has been more than a year since I started this FabAcademy journey, so my skills (and tools) have improved exponentially. I know some of the things I'm going to talk about might not seem interesting to some, but its my documentation, with the things I need to remember in the future, and the advices I would personally give to some one else.

The picture below, are some of the components I have bought during time for my "PabLab's" soldering station.

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"PabLab"
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Solder from smaller to bigger!

It is always better to start soldering the smaller, more complicated parts, and the go with the bigger, easier, faster parts.

So for example, if you have an FTDI or MicroUSB, you should better start with those, test them with a multimeter to see if they are not in short and that they are properly connected, and then continue with the rest.

Another good tip in this small parts is to first solder one leg and check that everything is in position, before soldering the rest. It is better if you also clean your tip for each leg you solder.

Another good tip, as long as you can choose, is to use trougholes instead of SMD pins (my preference), because they will grab harder from the PCB and last longer. But a better tip than that, is to solder your pins backwards whenever you can. For that sometimes you might even need to design it all backwards, but it worths it a lot, since that is going to help you a lot to solder your pins properly to the copper part, because if not, you will have to manage to get the soldering tip under the plastic female pinholes and you will probably burn them and also because they hold much harder.

Soldering Sucker

Soldering Wick
(Desoldering Wire)

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Some other problems you might have are:

EXCESS SOLDERING:
Which can be easily removed with a Solder Sucker or a Solder Wick. The soldering Sucker will help you remove overall excess by sucking the soldering when you charge it and press the button. While the soldering Wick needs you to add some soldering first over the wick, then put it over the part you want to desolder or clean, and press it with the tip of the iron so that it absorbes the excess of soldering.

COLD SOLDERING:
Your solder should end up shinny, because if not it might not have melted correctly and it will not grab so strong. This can also be caused by using a bad quality soldering, which melts pretty bad.

(Image Source ADAFRUIT)

COLD SOLDERING

SHINNY SOLDERING

Quality tools will save you time:

Time means money, and one of the thing I have learned by myself soldering at home, is that using good quality tools will save you a lot of time... and money in the end (or life).
At home I have a medium-low quality soldering kit, and even dough it does the work, it comes with a very "shitty" soldering wire, soldering tips and wire cutters... so after loosing a lot of time peeling wires, or soldering and desoldering with a bad quality soldering wire because it doesn't solder good or looks like cold soldered, I have upgraded some of the items in my "PabLab" and it has changed my life.

SOLDERING TIPS:
The soldering kit I bought comes with some low quality tips, that seem to be made of aluminium or other cheap material, and the problem with this is that the worn pretty fast (I have changed 3 of them in one single soldering session) and have bad heat dissipation, so the tip, which is supposed to be the part that heats, stops heating in the tip and starts heating in the sides. I changed them instead for new tips made out of iron, which also seem to have the rest of the structure covered with some protective material, and what makes the tip to still be the hot part.

I just started trying them few days ago, but at the moment, they work pretty good.

Aluminium Tips

Iron tips

Wire Cutters (pliers):
I learned from my dad that sometimes the easiest way to peel a wire is with fire (a lighter or a candle, and then removing it with the fingers)... but that does not look to profesional.
I got the yellow/orange wire peelers that you can see in the left with some flexible silicone wires I bought (pretty good by the way), but even dough they can work in a extreme case, it takes you a lot of time to peel the wires properly. So I just bought this new GUMPLA pliers and they are just amazing, you can cut different type of wires, measure screws and even clamp with them. I really recommend them because the end work is amazingly good.

Soldering Wire:
Same thing with the soldering wire... I got used to use the soldering wire at the FabLab, but during lockdown I had to solder some stuff at home with the soldering wire that came with my soldering kit, and I was getting a lot of cold soldering problems. One of the things is that since now most of the soldering wires come without (PLOMO) because of some safety restrictions, they don't solder as good as they did in the past. So there are different mixes of materials. So after spending my money buying soldering on "Chinnesse stores" that did not worked well or at a Amazon, I asked Edu at the FabLab BCN and he recommended me the one that appears in the middle of the picture, which is the one they use in there. It was like 4.95€ x 100gr and I just love it!!! You get a really good shinny fast soldering as an end result.

Cheap vs Good

Chino's / The Love of my life soldering wire / Amazon

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To solder, what I do is to touch the metallic/copper contact part of the board while touching also a little bit of the wire, so that they both heat up, and then, in the other side, I touch it with the soldering wire and it easily melts.

I have been trying with different temperatures for soldering, and I think that for my soldering iron and soldering wire, between 350º and 400º is pretty good.

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Test as you solder:
It is better to test every connection after making it, before continuing to the next one, because with that you will find the problems early and debug them faster than testing all connections after you have already soldered everything... and sometimes, when you soldered everything, it makes it more difficult to desolder small components or the ones that are very close to each other.

Bridging:
One thing I lately discovered is a good wat to bridge between two trough-holes, since when you have a coated board, the soldering will barely stick over the coated part, so what I do is to add a little bit of soldering directly to the iron to make a little ball, and then add the whole ball directly in the middle of the two connections and it bridges pretty good.

The other, more common way to bridge when needed or when you have a faulty connection could be with a wire or with a 0R when you have the bridging directly from your design,

8 - Machine Testing:

Testing the machine and end mill accuracy.

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For this test, I used the SRM-20 with a 1/64 end mill, usually used for the traces, to see how small it can make them.

I tested this with the line test file from Neils class, which is like a ruler that shows different line thickness so we can see how far the machine can go with a certain end mill, and by knowing that, we can also take that in count for the design rules we use to create our PCB designs.

The lower lines (created by removing material around the line) work pretty well down to .001, but instead, the upper lines (created by removing material from in between two lines), apparently where not detected by the software, so it did not cut them.

ESP8266 12-E Chip Pinout

I had to do 3 different tests because the bed was not properly calibrated or the PCB was not sticked well to the bed, so in the first pass, the machine left a lot of material. I also made a mistake the first time I created the file in mods because I let the offset in 4, what gives only one pass around the traces an leaves a lot of material.

ESP8266 12-E Chip Pinout

In the second test, I forced the Z axis home to be 0.10mm lower than the real home, and changed the offset of the file to -1 (for it to clean a lot more material). But the problem this time was that I forced the Z way to much, so this time it removed a lot of material from the PCB. Usually when I force the Z axis, I lower the machine Speed to 80%, I run the spindle and start lowering in small amounts until I see it starts peeling some cooper and white PCB material. Then I set it, and after that I lift it about 100 steps and then turn off the spindle (not before lifting it).

ESP8266 12-E Chip Pinout

So for my third try, I did it by forcing the Z home only 0.03mm and with -1 offset, so this time it removed it correctly, but anyway it did not do a smooth trace, probably because of my end mill or the amount of force, so it looks a bit rusty.

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